This is the fourth edition of this guideline. The first, published in 2001, was entitled Placenta Praevia: Diagnosis and Management; the second, published in 2005, was entitled Placenta Praevia and Placenta Praevia Accreta: Diagnosis and Management; and the third, published in 2011, was entitled Placenta Praevia, Placenta Praevia Accreta and Vasa Praevia: Diagnosis and Management.

Placenta praevia and placenta accreta are associated with high maternal and neonatal morbidity and mortality. The rates of placenta praevia and accreta have increased and will continue to do so as a result of rising rates of caesarean deliveries, increased maternal age and use of assisted reproductive technology (ART), placing greater demands on maternity-related resources. The highest rates of complication for both mother and newborn are observed when these conditions are only diagnosed at delivery.

Determining placental location is one of the first aims of routine midpregnancy (18+6 to 21+6 weeks of gestation) transabdominal obstetric ultrasound examination. A recent multidisciplinary workshop of the American Institute of Ultrasound in Medicine suggests that the term ‘placenta praevia’ is used when the placenta lies directly over the internal os. The estimated incidence of placenta praevia at term is 1 in 200 pregnancies.

Placenta accreta is a spectrum disorder ranging from abnormally adherent to deeply invasive placental tissue. Diagnostic difficulties probably explain the current wide variation in reported prevalence of placenta accreta ranging between 1 in 300 and 1 in 2000 pregnancies, and highlight the need for a standardised approach to imaging, clinical and histopathological descriptions.

The purpose of this guideline is to describe the diagnostic modalities and review the evidence-based approach to the clinical management of pregnancies complicated by placenta praevia and placenta accreta.

Declaration of interests

Professor ERM Jauniaux FRCOG, LondonProfessor in Obstetrics and Fetal Medicine, Professor Jauniaux is a departmental Graduate Tutor (taught) at the EGA Institute for Women's Health, Faculty of Population Health Sciences, University College London. Professor Jauniaux is the co-founder and trustee of Medical aid films [MAF] a UK-registered charity [no 1121578] which provides multi-media programs for medical education and training in developing countries (www.medicalaidfilms.org). In addition, Professor Jauniaux is the co-founder of Sonic Womb, a research collaboration with UCL which aims to understand and recreate the sound in utero in order to improve neonatal incubators for premature babies.

Professor Z Alfirevic FRCOG, Liverpool

Mr AG Bhide FRCOG, LondonNone declared.

Professor MA Belfort, Baylor College of Medicine, Houston, Texas, USA

Professor GJ Burton, University of Cambridge, UKNone declared.

Professor SL Collins MRCOG, Oxford, UKProfessor Collins is the Vice Chairman of the International Society for Abnormally Invasive Placenta.

Dr S Dornan, Royal Jubilee Maternity Hospital, Belfast, UK

Mr D Jurkovic FRCOG, London

Professor G Kayem, Armand-Trousseau and Louis-Mourier University Hospitals, Paris, FranceProfessor Kayem is a member of the French Perinatal Society. Professor Kayem is also the co-director of Axis 2 “maternal morbidity” of the EPOPE team, and the the principle investigator of the PACCRETA and TOCOPROM projects funded by the French Health Ministry.

Professor J Kingdom, Mont Sinai, Toronto University, Canada

Professor R Silver, University of Utah, Salt Lake City, Utah, USA

Professor L Sentilhes, University Hospital Angers, FranceProfessor Sentilhes receives lecture and consulting fees from Ferring, and lecture fees from Bayer, GSK and SIGVARIS. Professor Sentilhes is the main investigator of the TRAAP1 and TRAAP2 trials funded by the French Health Ministry.